[Themes] Add support for generating liquid and JSON section files

[jamesmengo]

WHY are these changes introduced?

Adds support for generating theme sections with both Liquid and JSON file types, providing developers with more flexibility when creating new theme sections.

WHAT is this pull request doing?

• Introduces a new generateSection service to handle section file creation
• Adds support for both Liquid and JSON section file types
• Implements file existence checks to prevent overwriting existing sections
• Updates the section generator command to handle the new file type option
• Adds comprehensive tests for the section generation functionality

How to test your changes?

1. Run theme generate section and follow the prompts
2. Choose between Liquid or JSON file types
3. Verify the generated section file contains the correct structure
4. Try generating a section with a name that already exists to test error handling

Measuring impact

• n/a - this doesn't need measurement, e.g. a linting rule or a bug-fix

Checklist

• I've considered possible cross-platform impacts (Mac, Linux, Windows)
• I've considered possible documentation changes

[jamesmengo]

• [Themes] Add TODOs for template generator improvements #5101
• [Themes] Remove template type flag and related functionality #5100
• [Themes] Add template generation with liquid and json support #5099
• [Themes] Add support for generating liquid and JSON section files #5090 👈 (View in Graphite)
• Feat: Generate Liquid Blocks #5088
• Add theme generation commands for blocks, sections, and templates #5081 : 1 other dependent PR (#5089 )
• Add --dev-preview flag to theme init for framework theme support #5079
• main

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[github-actions]

Unused types (3)

Filename	types
packages/theme/src/cli/services/generate/blocks.ts	BlockGeneratorOptions
packages/theme/src/cli/utilities/generator.ts	TemplateType
packages/theme/src/cli/services/generate/sections.ts	SectionGeneratorOptions

[github-actions]

Coverage report

St.❔	Category	Percentage	Covered / Total
🟡	Statements	75.27%	8780/11664
🟡	Branches	70.57%	4280/6065
🟡	Functions	74.98%	2295/3061
🟡	Lines	75.83%	8301/10947

Test suite run success

1981 tests passing in 896 suites.

Report generated by 🧪jest coverage report action from 9a241ab

[david-w-shopify]

Had a very quick play with this. A couple of comments

1. I'd expect section groups (JSON sections) to be a separate command. Despite existing inside /sections they're so different to liquid sections that I wouldn't expect them to share a command. It would also remove an extra step from the section command which is a nice win. In my experience in agencies building Shopify themes - new Liquid sections are regularly created, JSON section groups are rarely created
2. It would be nice to include a type field when generating the section group to populate that field in the schema. Perhaps if the user doesn't use header, footer or aside we could automatically prefix it with custom. too

[david-w-shopify]

Both section filename and schema "name" property match. This will result in users changing one or the other almost every time this command is used. I'd recommend converting the name to kebab case for the filename